Arrange these compounds in order of increasing acidity: 2,4-dichlorophenol, phenol, cyclohexanol.

The first step in comparing the acidity of the three compounds is to identify the acidic proton in each molecule, which is typically the most labile proton bonded to the most electronegative atom. In 2,4-dichlorophenol and phenol, the acidic protons are the hydroxyl protons (OH) bonded to the benzene ring. In cyclohexanol, the acidic proton is also the hydroxyl proton (OH) bonded to the cyclohexane ring.

After a compound donates its acidic proton, it forms a conjugate base with a negative charge. Comparing the stability of the conjugate bases will help us predict the relative acidity of these compounds. A more stable conjugate base implies that the original compound is more acidic. For 2,4-dichlorophenol, the conjugate base will have a negative charge on the oxygen atom, with the two chlorine atoms on the benzene ring. For phenol, the conjugate base will also have a negative charge on the oxygen atom. For cyclohexanol, the conjugate base will have a negative charge on the oxygen atom as well.

Now, we need to compare the electronic effects that stabilize the conjugate bases. Two primary effects to consider are resonance delocalization and the inductive effect of electron-withdrawing groups. In 2,4-dichlorophenol, the negative charge on the oxygen atom can be delocalized via resonance through the benzene ring. Additionally, the chlorine atoms withdraw electron density through an inductive effect, further stabilizing the conjugate base. In phenol, the negative charge can also be delocalized via resonance through the benzene ring, but there are no electron-withdrawing groups to stabilize the conjugate base. In cyclohexanol, the negative charge cannot be delocalized as the aliphatic ring does not have a π system, making its conjugate base the least stabilized of the three.

Based on the stability of their conjugate bases, we can arrange the given compounds in order of increasing acidity: 1. Cyclohexanol (least acidic) - due to the lack of resonance stabilization and electron-withdrawing groups. 2. Phenol - due to resonance stabilization but no electron-withdrawing groups. 3. 2,4-dichlorophenol (most acidic) - due to resonance stabilization and the presence of electron-withdrawing chlorine atoms. So, the order of increasing acidity is: Cyclohexanol < Phenol < 2,4-dichlorophenol.